IGF plays an important role in the regulation of the proliferation, differentiation and cell death (apoptosis) of epithelial cells in organs such as breast, prostate, lung, and colon. The biological activity thereof is mediated by the IGF receptor (referred to as IGF-R hereinafter) (Endocrine Reviews, 16, 3, 1995). Additionally, there exist 10 types of IGF-binding proteins (referred to as IGFBP hereinafter) which not only suppress IGF metabolism but also regulate transferring of IGF and binding with the IGF receptors (Journal of Biological Chemistry, 264, 11843, 1989).
IGF includes two types, IGF-I and IGF-II, comprising a single chain polypeptide. Both of them have 40% homology with an insulin precursor proinsulin at the amino acid level (Advances in Cancer Research, 68, 183, 1996). In intravital, insulin receptor, IGF-I receptor (hereinafter referred to as IGF-R), IGF-II receptor (hereinafter referred to as IGF-IIR) and hybrid receptors of the insulin receptor and IGF-R is acting as the receptors of IGFs.
The insulin receptor and the IGF-R are both tyrosine kinase-type receptors (Endocrine Reviews, 16, 143, 1995, Breast Cancer Research & Treatment, 47, 235, 1998). At the amino acid levels, both of them have an about 60% homology. Each of the insulin receptor and the IGF-R have a high binding specificity to their specific ligands, namely insulin and IGF-I but they also have a binding property to insulin, IGF-I or IGF-II (Journal of Biological Chemistry, 263, 11486, 1988, Journal of Biological Chemistry, 268, 7393, 1993), respectively. Further, it is considered that hybrid receptors comprising each subunit of insulin receptor and IGF-R have higher binding specificities to IGF-I than to insulin and act as IGF-R. However, the biological functions thereof are unknown (Endocrine Reviews, 16, 3-34, 1995, Endocrine Reviews, 16, 143, 1995). IGF-IIR can bind to IGF-II alone in the IGF family. Since IGF-IIR has no tyrosine kinase activity, it is considered that IGF-IIR may act as an IGF-II antagonist (Proceedings of the National Academy of Sciences of the United States of America, 94, 12981, 1997). As described above, the 2 types of IGFs form complex networks with the 10 types of IGF-binding proteins (hereinafter referred to as IGFBP) in addition to these 4 types of receptors, and are acting in intravital.
It is known that IGF is expressed in a wide variety of cancers such as sarcoma, leukemia, prostate cancer, breast cancer, lung cancer, colon cancer, gastric cancer, esophagus cancer, hepatic cancer, pancreatic cancer, renal cancer, thyroid gland cancer, brain tumor, ovarian cancer and uterine cancer, and IGF has a strong proliferation-promoting activity for these cancer cells (British Journal of Cancer, 65, 311, 1992, Anticancer Research, 11, 1591, 1991, Annals of Internal Medicine, 122, 54, 1995, Oncology, 54, 502, 1997, Endocrinology, 137, 1764, 1996). Also, it is known that IGF-II and IGF-R are more highly expressed in highly metastatic cancers than in poorly metastatic cancers (International Journal of Cancer, 65, 812, 1996). It is therefore suggested that IGF may be in cancer metastasis. The IGF promoting cell proliferation activity is mainly mediated by IGF-R (Endocrinology, 136, 4298, 1995, Oncogene, 28, 6071, 1999). However, it is also known that IGF-II acts through insulin receptor in some types of breast cancer cells (Oncogene, 18, 2471, 1999).
Clinical and epidemiological examinations have issued reports about the increase of IGF or IGF-R level in many cancer tissues such as breast cancer (Cancer Epidemiology, Biomarkers & Preventions, 11, 1566, 2002, European Journal of Cancer, 29A, 492, 1993), neuroblastoma, lung cancer (Journal of the National Cancer Institute, 92, 737, 2000), colorectal cancer (Gut, 44, 704, 1999), prostate cancer (Cancer Research, 62, 2942, 2002, Science, 279, 563, 1998), ovarian cancer (International Journal of Cancer, 101, 549, 2002), bladder cancer (Journal of Urology, 169, 714, 2003) and osteosarcoma or in serum IGF level (Journal of the National Cancer Institute, 92, 1472, 2002). Further, it is reported that cancer patients with IGF-R expression have poor prognosis (Cancer Research, 57, 3079, 1997).
It is known that the cell death of colorectal cancer cells as induced by interferon or tumor necrosis factor with an cell death-inducing activity is suppressed by IGF-I. It is additionally known that compared with radiologically sensitive cancer cells in primary culture cells derived from glioblastoma patients, the expression levels of IGF-IR and phosphorylated IGF-IR in radiologically resistant cancer cells therein are increased and that when the functions of receptors of the epidermal growth factor in the radiologically sensitive cancer cells are inhibited, it is known that the IGF-R expression levels increased. The above findings reveal that IGF has an effect of promoting the proliferation of cancer cells but also is involved in the enhancement of the survival signal of cancer cells via IGF-R to allow the cancer cells to acquire drug resistance (Journal of the National Cancer Institute, 93, 1852, 2001, Oncogene, 20, 1913, 2001, Cancer Research, 60, 2007, 2000, Cancer Research, 62, 200, 2002).
Further, as the diseases other than cancers, diseases related with IGFs are reported. Among gigantism and acromegaly, it is also considered that abnormal IGF expression caused secondarily by abnormal growth hormone secretion is therefore involved in the progress of the pathology (Growth Hormone & IGF Research, 13, 98, 2003). Additionally, IGF-I involvement is also suggested in diabetic complications (Science, 276, 1706, 1997, American Journal of Physiology, 274, F1045, 1998) and the onset of the pathology of rheumatoid arthritis (Journal of Clinical Endocrinology & Metabolism, 81, 150, 1996, Arthritis & Rheumatism, 39, 1556, 1996).
Research works using model animals have been made to examine the relations between IGF and various diseases. It is known that in human prostate cancer-grafted model mice, as the mice acquire an androgen-independent proliferation, IGF-I and IGF-R expression levels increase (Cancer Research, 61, 6276, 2001). Additionally, most of serum IGF is generated in liver. It is known however that serum IGF is involved in cancer growth since the growth of colorectal tumor orthotopically grafted in IGF-I deficient-mice of in liver alone is suppressed (Cancer Research, 62, 1030, 2002). Cancer development or hypertrophy is observed in mice which expresses of IGF at specific focus in intravitals (Oncogene, 22, 853, 2003, Cancer Research, 60, 1561, 2000, Journal of Biological Chemistry, 269, 13779, 1994).
As described above, IGF, IGF-R and IGFBP play important roles not only in development, growth and metastasis of cancer but also in acromegaly, diabetic complications, rheumatoid arthritis and the like.
Anti-tumor effect which inhibits the signal transduction between IGF and IGF-R has been examined so far. It is reported that anti-IGF-IR antibodies targeting IGF-IR (Cancer Research, 63, 5073, 2003, WO 02/53596), IGF-R inhibitors (WO 99/28347) or IGFBP capable of inhibiting serum IGF can demonstrate an anti-tumor effect in animal models (Cancer research, 62, 3530, 2002).
Although the anti-IGF-IR antibodies can inhibit the engraftment of human breast cancer cells with estrogen-independent growth as grafted in mice, it is revealed that the antibodies do not suppress the engraftment of human breast cancer cells with estrogen-dependent proliferation or the proliferation of the engrafted human breast cancer cells. It is thus revealed that the inhibition of the function of IGF-IR alone does not provide sufficient anti-tumor effect (Breast Cancer Research & Treatment, 22, 101, 1992).
Various antibodies are known as antibodies against IGF (hereinafter referred to as anti-hIGF antibodies). Typical antibodies against human IGF-I (hereinafter referred to as anti-hIGF-I antibodies) include anti-hIGF-I mouse antibody sm1.2 (Proceedings of the National Academy of Sciences of the United States of America, 81, 2389, 1984). Antibodies against human IGF-II (hereinafter referred to as anti-hIGF-II antibodies) include anti-hIGF-II mouse antibody S1F2 (Endocrinology, 124, 870, 1989). sm1.2 has 40% crossreactivity with IGF-II, while S1F2 has about 10% crossreactivity with hIGF-I. It is known that both antibodies can inhibit hIGF-I- or hIGF-II-dependent cell proliferation in vitro.
When an antibody of a non-human animal, such as a mouse antibody is administered to human, the mouse antibody is recognized as a foreign substance. The administered antibody not only initiates side effects but also disappears rapidly. Therefore, the antibody is not useful for therapy. In order to solve these problems, attempts have been made to convert an antibody of a non-human animal into a humanized antibody, such as a human chimeric antibody or a human complimentarity-determining region (hereinafter referred to as CDR)-grafted antibody, using genetic engineering techniques. The human chimeric antibody is an antibody wherein the variable region (hereinafter referred to as V region) is an non-human animal antibody and the constant region (hereinafter referred to as C region) is a human antibody (Proceedings of the National Academy of Sciences of the United States of America, 81, 6851, 1984), and the human CDR-grafted antibody is an antibody wherein the amino acid sequences of CDRs in the V region of a non-human animal antibody of is grafted into an appropriate position of a human antibody (Nature, 321, 522, 1986). Compared to a non-human animal antibody, such as mouse antibodies, these humanized antibodies are more advantages in clinical use. With respect to immunogenicity and stability in blood, for example, a report tells that when administered to human, the half-life in blood of human chimeric antibodies has been extended an about 6-fold, in comparison with those of mouse antibodies (European Journal of Cancer, 29A, 492, 1993). It is also reported that human CDR-grafted antibodies, the immunogenicity has decreased in experiments using monkeys, and the half life in blood has extended compared with mouse antibodies (Cancer Research, 56, 1118, 1996, Immunology, 85, 668, 1995). Compared to non-human animal antibodies, it is expected that humanized antibodies have less side effects and have a therapeutic effect for a longer time. Additionally because the humanized antibodies are prepared by genetic engineering techniques, such humanized antibodies can be prepared as molecules having various forms. Due to the recent advances in protein engineering and genetic engineering, antibody fragments having a smaller molecular weight such as Fab, Fab′, F(ab′)2, scFv (Science, 242, 423, 1988), dsFv (Molecular Immunology, 32, 249, 1995) and CDR-containing peptide (Journal of Biological Chemistry, 271, 2966, 1996) can be prepared from antibodies including humanized antibodies. Because these antibody fragments have a smaller molecular weight than whole antibody molecules, these antibody fragments have superior transitional activity into target tissues (Cancer Research, 52, 3402, 1992).